INVESTIGATIONS ON RUBBER-BEARING PLANTS: III. DEVELOPMENT OF NORMAL AND ABORTING SEEDS IN ASCLEPIAS SYRIACA L.

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Abstract
A low percentage (2 to 3%) of the flowers of Asclepias synaca L. produce mature seed pods. Many ovaries begin to enlarge but abort before reaching maturity. Histological examination of these pods shows that ovule abnormalities accompany pod collapse. Ovules in free-nucleate endosperm stages show a growth of the integument that is excessive for ovules at this stage of embryo sac development. Older aborting ovules contained a zone of collapsed cells completely enclosing the endosperm.Seed collapse of the former type at least appears similar to cases attributed to a competition for food between endosperm and the adjacent maternal tissue of the ovule, termed "somatoplastic sterility" by Brink and Cooper.